Electronic Supplementary Material 2 - Additional observations in nature video-stenolemus breaks thread using the cautious tactic video-placement of middle leg on web from Fine-scale analysis of an assassin bug's behaviour: predatory strategies to bypass the sensory systems of prey
2016-10-18T13:10:20Z (GMT) by
Some predators sidestep environments that render them conspicuous to the sensory systems of prey. However, these challenging environments are unavoidable for certain predators. <i>Stenolemus giraffa</i> is an assassin bug that feeds on web-building spiders; the web is the environment in which this predator finds its prey, but it also forms part of its preys' sophisticated sensory apparatus, blurring the distinction between environment and sensory systems. <i>Stenolemus giraffa</i> needs to break threads in the web that obstruct its path to the spiders, and such vibrations can alert the spiders. Using laser vibrometry, this study demonstrates how <i>S. giraffa</i> avoids alerting the spiders during its approach. When breaking threads, <i>S. giraffa</i> attenuates the vibrations produced by holding on to the loose ends of the broken thread and causing them to sag prior to release. In addition, <i>S. giraffa</i> releases the loose ends of a broken thread one at a time (after several seconds or minutes) and in this way spaces out the production of vibrations in time. Furthermore, <i>S. giraffa</i> was found to maximally reduce the amplitude of vibrations when breaking threads that are prone to produce louder vibrations. Finally, <i>S. giraffa</i> preferred to break threads in the presence of wind, suggesting that this araneophagic insect exploits environmental noise that temporarily impairs the spiders' ability to detect vibrations. The predatory behaviour of <i>S. giraffa</i> seems to be adaptated in intricate manner for bypassing the sophisticated sensory system of web-building spiders. These findings illustrate how the physical characteristics of the environment, along with the sensory systems of prey can shape the predatory strategies of animals.